The molecular basis of pulmonary fibrosis remains unknown. The proposed studies will quantify the rate of collagen synthesis and the types of collagen synthesized in fibroblasts obtained from biopsy tissue and by bronchopulmonary lavage from the lungs of patients with pulmonary fibrosis. Comparisons will be made with low-passage IMR-90 and WI-38 human fetal lung fibroblasts and with lung fibroblasts from patients without fibrosis. These studies will quantify the amounts of collagen mRNA as a measure of the cell's ability to synthesize collagen. mRNA Fractions will be isolated and their ability to direct the synthesis of collagen determined. Collagen mRNA will be purified from collagen synthesizing polysomes immunoprecipitated with anti-collagen antibodies. Complimentary DNA (cDNA) to purified collagen mRNA will be synthesized using AMV RNA-directed DNA polymerase. This cDNA will be used in RNA-excess hybridization experiments to quantify the amount of collagen mRNA and in DNA-excess hybridization experiments to determine gene dosage. The studies will define the possibility that fibroblasts isolated from patients with fibrosis have an altered capacity to synthesize collagen which will lead to elucidating cellular pathogenic mechanisms of fibrosis. The effect of glucocorticoids on collagen synthesis in fibrosis cells will be examined in the context of literature data indicating that there are antianabolic effects of steroids on collagen metabolism and data from this laboratory indicating that this effect is selective for collagen synthesis. The proposed studies will determine the amount of collagen mRNA, the gene dosage and the type of collagen synthesized in fibrosis cells treated with glucocorticoid. The studies will provide fundamental new knowledge on the molecular biology of fibroblast collagen synthesis and the actions of glucocorticoids on that process. The latter will define a mechanism for the beneficial action of steroid therapy in pulmonary fibrosis.